There have been many suicide bomber attacks using vehicle borne improvised explosive devices (VBIED) over the past two decades, which have resulted in a huge loss of life. The typical tactic employed by the terrorist group is to load a vehicle with low cost explosives and drive to a political target, such as an embassy, military base, sports event, etc. Most attacks of this type have used between 250 and 2000 pounds of explosives concealed in the vehicle. To mitigate the damage from this type of attack, it is necessary to detect and deter the vehicle well before it enters the target area.
The Alcohol, Tobacco and Firearms website lists explosive payload based on vehicle size and type. For example, a compact sedan can carry up to 500 pounds of explosives; whereas a passenger van or cargo van can carry up to 4000 pounds. Some early VBIED threats were easily identified because the heavy explosive payload caused the vehicle to ride very low on its suspension. Since that time terrorists have learned to add (i.e., weld) additional support to the suspension under the heavy explosives so that the vehicle appears to ride normally.
Commercial axle scales have been developed primarily for use as truck scales for enforcing highway load limits. Traditional truck scales have used large platforms to measure multiple axles while the vehicle is stopped on the scale. More recently, weigh-in-motion (WIM) systems have been developed to allow the vehicles to continue moving over the scale without stopping. Some systems, like the Fairbanks Model 4020, require the vehicle to slow to less than 5 miles per hour (mph) while others, like the IRD Bending Plate WIM Sensor can measure a weight of a vehicle when the vehicle is at full highway speed. The WIM scales measure each axle separately or, in some cases, each tire separately. Thus, commercial axle scales and WIM scales provide examples of a number of different means for determining a vehicle weight. Commercial axle scales may be more effectively utilized at border crossings where custom's officials have the task of determining which vehicles should be subjected to detailed inspection to uncover illegal drug or commercial trafficking and/or terrorist threat.